Painting DensShield

Q.I'd like to use a coated
glass mat tile backerboard like DensShield in a shower
stall, but would like to stop the tile about 78 inches
above the floor rather than completely covering the
walls and ceiling. Is it okay to continue the
backerboard all the way up to the 8-foot-high ceiling
— which would be covered with the same
material — and then simply paint the nontiled
areas? If so, how should the textured surface of the
tile backer be prepped for a smooth, painted
finish?

A.Charles Young, a
technical service representative with
Georgia-Pacific Gypsum in Atlanta, responds:
In a typical residential shower, it is acceptable
to skim-coat DensShield tile backer
(Georgia-Pacific Gypsum, 800/225-6119,
www.gp.com/build) with a
setting-type joint compound — such as
Durabond (USG, 800/874-4968, www.usg.com) or
Georgia-Pacific's ToughRock 45 or 90 — to
get a smooth, paintable surface in areas that
aren't tiled.

Since these compounds set by a chemical reaction
and are very hard when they cure, you might be
tempted to use a sandable version. But sandable
setting compounds are not recommended in this
application, because they don't set as hard as
regular formulations. Use 2-inch 10x10 glass-fiber
mesh tape (not paper tape) at the corners and
wherever DensShield butts into regular gypsum board
outside the shower. Joints to be covered with tile
should be skimmed with the same latex-modified
thinset mortar or Type 1 mastic that will be used
to set the tile; otherwise, skim the joints with
setting compound.

The nontiled areas can be primed and painted
with the same finish used on the other walls in the
room as long as the primer and paint are suitable
for high-moisture areas.